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A team of researchers at MIT have developed a rather clever new twist on the conventional powered exoskeleton idea*. Rather than seeking to amplify the strength of the wearer's own muscles, the relatively simple MIT rig is intended merely to transfer the load of a heavy backpack directly to the ground, which allows very low power consumption.

As keen backpackers and foot soldiers are well aware, a person carrying a heavy load uses up a lot of energy merely keeping his pack up off the ground, quite apart from that needed to move it along. This is why those suitcases with the little wheels are so popular, too; but they aren't practical away from nice smooth surfaces. It seems that the MIT team are looking to tackle this issue in the offroad environment, funded by the Defence Advanced Research Projects Agency (DARPA), the mentally box-averse Pentagon boffin bureau.

Man, this tiny backpack sure is deceptively heavy.

The MIT exoskeleton rig consists of a pair of boots with tubular struts running up alongside the leg to the backpack. Most of the weight rides on springs and dampers, the load being effectively jacked up off the ground for the wearer. Actuators come into play merely to make the exoskeleton follow the wearer's leg rather than assist it. This means that the device uses only one watt of power.

Reporting on their work in this month's issue of the International Journal of Humanoid Robotics, the MIT researchers say that the machinery can take 80 per cent of an 80 pound backpack load. However, they admit that it impedes the user's freedom of movement.

"You can definitely tell it's affecting your gait," according to Conor Walsh, a grad student who worked on the project. Even so, "you do feel it taking the load off and you definitely feel less stress on your upper body."

A sole watt of power is far from an outrageous demand in the context of modern soldiering; the Pentagon are hoping to achieve portable tech which will let a footsore grunt carry 1920 watt-hours in his gear. The MIT leg-boinger rig looks a bit more sensible than the petrol-engined "Bigdog" robo-packmule.

That said, foot marching with heavy kit as a dedicated activity is rather going out of military fashion. Soldiers still need to be able to carry heavy gear, but these days it isn't so much because they have to hump rations, tents, bedding etc from bivouac to bivouac; it's because their basic combat load has become so heavy. They're carrying body armour, weapons and electronics nowadays, and they need to be able to react and fight, not simply trudge. That could be a bit difficult with their legs strapped into a restrictive spring suspension rig.

But it's early days yet for the MIT team and their kit. According to Walsh, they're looking to refine the gear a lot before offering it for any military trial.

"This is the first time that it has been tested," he said. "We didn't know what to expect."

*Conventional to Reg readers and sci-fi fanciers, anyway. For those newcomers who have failed to acquire a basic classical education, an exoskeleton in this sense is basically a powered mechanical suit which can enhance the wearer's strength and/or speed. Recommended reading/viewing: Starship Troopers, Aliens etc.